1. Technical Field
A light-emitting diode (LED) device and manufacturing methods thereof are provided, and more particularly to a LED device having a three-dimensional electron cloud structure and/or a three-dimensional hole cloud structure and manufacturing methods thereof.
2. Reference to Related Application
This application claims the right of priority based on TW application Ser. No. 096130660, filed Aug. 17, 2007, entitled “LIGHT-EMITTING DIODE DEVICE AND MANUFACTURING METHOD THEREOF”, and the contents of which are incorporated herein by reference.
3. Description of the Related Art
The light-emitting diodes (LEDs) of the solid-state lighting elements having the characteristics of low power consumption, low heat generation, long operational life, shockproof, small volume, quick response and good opto-electrical property like emitting stable wavelength and so on, so that the LEDs have been widely used in household appliances, indicator light of instruments, optics and photonics products, etc. As the optics and photonics technology develops, the solid-state lighting elements have great progress in increasing the light efficiency, operation life and the brightness. LEDs become the main stream of the lighting devices in the near future.
FIG. 1 shows a cross-sectional view of conventional light-emitting diode device 100. The conventional light-emitting diode device includes a substrate 101, an n-type semiconductor layer 102 epitaxially grown on the substrate 101, an active layer 103, a p-type semiconductor layer 104, a front side electrode 105 and a back side electrode 106 wherein the front side electrode 105 is disposed on the light extraction side of the light-emitting diode device 100 and the back side electrode 106 is formed on the side of the substrate 101 where no epitaxial structure formed on. The driving current R1 is driven from the front side electrode 105 to the p-type semiconductor layer 104, and through the active layer 103 having a double heterostructure or a multiquantum well to emit light. Generally speaking, in order to improve the light efficiency of the light-emitting diode device 100, the current from the front side electrode 105 needs to be spread to the edge of the light-emitting diode device 100 effectively to make the active layer 103 emitting light uniformly.
Because of the high contact resistance between the semiconductor layer and the metal electrode of the light-emitting diode device 100, the current R1 cannot spread to the active layer 103 effectively. The current R1 will flow with the shortest pathway passing through the active layer 103 to the back side electrode 106 and the current crowding effect is therefore occurred. It makes the lighting area limited in a portion of the active layer 103 below the front side electrode 105, and greatly influences the light efficiency of the active layer 103.
In order to solve the issue described above, a conventional technique is to form a layer on the most top layer of the epitaxial stack in the light-emitting diode device 100, wherein the layer can be a window layer with low electrical resistance, a current blocking layer or a transparent electrode layer formed by ITO to make the current R1 spread uniformly from the front side electrode 105. The current can also be spread by changing the structure or the layout of the front side electrode 105, and the light efficiency of the light-emitting diode device 100 is therefore enhanced.
However, additional process steps are required no matter what techniques are adopted. Thus the manufacturing cost is increased, the LED quality is damaged, and the yield is decreased.
Therefore, a light-emitting diode having efficient current spreading and better light efficiency with simpler processes is needed.